title: Daily step count is associated with plasma C-reactive protein and IL-6 in a US cohort with COPD.
abstract: BACKGROUND
  Physical activity is an important clinical marker of disease status in COPD. COPD is also characterized by low-grade systemic inflammation. However, the relationship between physical activity and systemic inflammation in COPD is unclear.
  
  
  METHODS
  We monitored daily step count, a directly measured physical activity, using the StepWatch Activity Monitor, an ankle-worn accelerometer, in 171 people with stable COPD. Exercise capacity was assessed with the 6-min walk test (6MWT). We measured plasma C-reactive protein (CRP) and IL-6 levels. Linear regression models examined the cross-sectional associations of daily step count and 6MWT distance with CRP and IL-6 levels.
  
  
  RESULTS
  Subjects had a mean age 72±8 years and mean FEV1 1.5±0.57 L (54±20% predicted). Median daily step count was 5,203 (interquartile range [IQR], 3,627-7,024], CRP level was 2.4 mg/L (IQR, 1.2-5.0), and IL-6 level was 2.9 pg/mL (IQR, 2.0-5.1). Each 1,000-step increase in daily step count was associated with a 0.94 mg/L and 0.96 pg/mL decrease in CRP (P=.020) and IL-6 (P=.044) levels, respectively, adjusting for age, FEV1 % predicted, pack-years smoked, cardiac disease, current statin use, history of acute exacerbations, and season. There was a significant linear trend of increasing daily step count by quartiles and decreasing CRP (P=.0007) and IL-6 (P=.023) levels. Higher 6MWT distance was also significantly associated with lower CRP and IL-6 values.
  
  
  CONCLUSIONS
  People with COPD who walked the most had the lowest plasma CRP and IL-6 levels. These results provide the conceptual basis to study whether an intervention to promote walking will reduce systemic inflammation in people with COPD.
authors.affiliation: Department of Veteran Affairs, Veterans Health Administration, Rehabilitation Research and Development Service, Boston, MA; Pulmonary and Critical Care Medicine Section, VA Boston Healthcare System, Boston, MA; Division of Pulmonary and Critical Care Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA; Harvard Medical School, Boston, MA. Electronic address: marilyn.moy@va.gov.
authors.forename: Marilyn L
authors.initials: ML
authors.lastname: Moy
authors.affiliation: Pulmonary and Critical Care Medicine Section, VA Boston Healthcare System, Boston, MA.
authors.forename: Merilee
authors.initials: M
authors.lastname: Teylan
authors.affiliation: Pulmonary and Critical Care Medicine Section, VA Boston Healthcare System, Boston, MA; Department of Biostatistics, Boston University School of Public Health, Boston, MA.
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Weston
authors.affiliation: VA Cooperative Studies, Boston, MA.
authors.forename: David R
authors.initials: DR
authors.lastname: Gagnon
authors.affiliation: Pulmonary and Critical Care Medicine Section, VA Boston Healthcare System, Boston, MA; Department of Epidemiology, Brown University, Providence, RI.
authors.forename: Valery A
authors.initials: VA
authors.lastname: Danilack
authors.affiliation: Department of Veteran Affairs, Veterans Health Administration, Rehabilitation Research and Development Service, Boston, MA; Pulmonary and Critical Care Medicine Section, VA Boston Healthcare System, Boston, MA; Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA; Harvard Medical School, Boston, MA.
authors.forename: Eric
authors.initials: E
authors.lastname: Garshick
mesh_terms: D061725:Accelerometry / Q000379:methods*; D000368:Aged; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism*; D003430:Cross-Sectional Studies; D017079:Exercise Tolerance; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015850:Interleukin-6 / Q000097:blood*; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D011379:Prognosis; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood / Q000503:physiopathology*; D012189:Retrospective Studies; D016138:Walking / Q000502:physiology*
chemical_list: D015415:Biomarkers; D015850:Interleukin-6; D002097:C-Reactive Protein